Vacuum precooling condensate system



Nov. 1, 1955 c. R. ANDERSON VACUUM PRECOOLING CONDENSATE SYSTEM Filed May 29, 1953 INVENTOR. CHESTER 2. flNDEBSON .41 array United States Patent VACUUM PRECOULING (JONDENSATE SYSTEM Chester R. Anderson, Los Angeles, Calif. Application May 29, 1953, Serial No. 358,444 4 Claims. (Ci. 62169) This invention relates to an apparatus for vacuum precooling perishable products, and more particularly to an improved condensate system for improving the overall efiiciency of the apparatus.

It is conventional practice to precool perishable products after they have been harvested to inhibit their deterioration between the harvesting points and the ultimate points of sale. A preferred system for insuring uniform precooling of such products employs a suitable retort chamber for housing the products, which is evacuated to a pressure corresponding to about 29 inches of mercury causing the perishables to be uniformly cooled due to the flashing or evaporation of moisture therein. That is to say, as the pressure within the retort chamber is reduced, the temperature at which evaporation takes place is correspondingly reduced the evaporation itself serving to remove heat from the products. This cooling is absolutely uniform throughout the entire bulk of the product. Therefore when the vacuum is broken and the crated perishables are removed from the chamber, they will retain for a reasonable length of time this .precooled temperature.

In a preferred process for vacuum precooling, the evaporated moisture during the evacuating process, is caused to pass into a refrigerated condenser chamber where condensation of the vapor takes place, the condensate liquid flowing down a condensate pipe leading out from the bottom of the condenser under the influence of gravity. This condensate pipe terminates in a storage or liquid condensate tank provided With a suitable drain outlet for flushing at certain intervals.

Since the condensate tank, condenser chamber, and retort chamber housing the perishable products, are all in communication with one another through connecting conduits, both the condenser chamber and condensate tank will assume the same reduced pressure existing in the retort chamber. This pressure varies between 29.18 and 29.74 inches of mercury at which pressures moisture will flash or evaporate at corresponding temperatures ranging from 70 to 33 F.

The temperature within the refrigerated condenser chamber is generally lower than 33 F. and therefore condensation of the moisture is effected without any difliculty. When the condensate liquid reaches the lower condensate collecting tank however, it tends to approach a higher temperature as it becomes further removed from the condenser. Since the condensate tank is at the same reduced pressure as exists in the retort, there is accordingly a tendency for the liquid to re-evaporate and pass back up to the condenser chamber. This re-evaporation lowers the general overall efliciency of the system in two respects. First, the re-evaporation will cool the sides of the condensate pipe leading from the condenser chamber to the collecting tank and can result in sufiicient frost accumulating to plug the pipe. Second, the re-evaporated moisture flashing back up into the condenser chamber together with the evaporated moisture from the perishables in the retort will result in a much larger amount of 2,722,112 Patented Nov. 1, 1955 vapor in the condenser chamber than can be efiiciently handled. In the event the refrigeration is effected by several turns of refrigeration pipes, this additional quantity of vapor will cause a frost to build up on the pipes more quickly than would be the case were the only vapor to be handled that derived from the perishables in the retort. The accumulation of frost on the refrigeration pipes acts as an insulator about the pipes and will thus lower their efliciency.

The present invention relates to an apparatus for vacuum precooling perishable products having as its principal object provision of an improved condensate collecting system in which the aforementioned difiiculties are overcome.

More particularly, it is an object of the invention to provide means in combination with a vacuum precooling apparatus for substantially preventing condensate liquid from flashing back into the condenser chamber.

These and additional objects and advantages of the invention are attained by incorporating a check valve in the condensate pipe leading from the condenser chamber to the condensate tank. This valve is designed for automatic operation to open only when liquid condensate is coming down the pipe, and to remain closed at all other times thereby sealing the pipe against back flashing of the liquid condensate. The invention additionally contemplates in the condensate system, a small bleeder line connected between the condensate tank and retort chamber containing the perishable products, to prevent a pressure differential from developing between the two chambers which would tend to retain the check valve in closed position.

A better understanding of the apparatus will be had by referring to the accompanying drawings in which:

Fig. 1 shows in schematic perspective form a preferred embodiment of the vacuum precooling system; and

Fig. 2 is an enlarged view partly in section of the check valve employed in the condensate system.

As shown in Fig. 1, there is provided a retort chamber 10 into which various crates of perishable products 11 are placed. Ordinarily several of these retorts are located side by side in order to permit processing several crates of perishables simultaneously. The perishables 11 are moved into the retort by dolly trucks 12, both ends of the retort being hermetically sealed by suitable doors (not shown).

Disposed above the retort chamber 10 is a centrifugal type blower 13 having an inlet conduit 14 communicating with the retort 10 and an outlet conduit 15 passing into the lower end of a rectangularly shaped condenser chamber 16. Condenser chamber 16 includes a plurality of refrigeration pipes 17 suitably connected to a refrigeration pump 18 as shown.

A vacuum pump 19 communicates with the condenser chamber 16 by means of a manifold of conduits 20 merging into a main conduit 21 connecting to the vacuum pump 19 and including a further conduit 22 terminating in a valve 23 adapted to be opened to the atmosphere.

From a lower end portion of the condenser chamber 16, there is provided a condensate pipe 24 sloping down at a small angle, for passing condensate liquid from the condenser chamber through a check valve 25, conduit 26, to a condensate collecting tank 27. The tank 27 is provided with a condensate drain 28 having a suitable shutoff valve as shown. A small bleeder line 29 between the condensate tank 27 and the retort 10 is provided for equalizing the pressure in the condensate tank27 and retort 10 the reason for which will become clear as the description proceeds.

In the vacuum precooling process, the perishable prod ucts 11 are rolled on the dollies 12 into the retort 10, the ends of the retorts being hermetically sealed. Power 14, outlet conduit 15, manifold conduits 20, and main,

conduit 21. After five or six minutes of operation the pressure within the retort is reduced to a value corresponding to approximately 29.18 inches of mercury. At this pressure, moisture will flash or be evaporated at a temperature of about 70 F. At this pressure, power to the blower 13 is supplied to remove the evaporated flashed moisture from the retort to the condenser chamber 16. Simultaneously the refrigeration pump 18 is caused to operate. The reason for starting the blower 13 only after a predetermined low pressure has been reached is that considerably less power is needed to rotate the centrifugal blower at this low pressure.

Evaporated moisture from the perishables will be passed over the refrigeration pipes 17 within the condenser 16 condensing out on the pipes and falling to the bottom of the condenser chamber. This moisture will then, by gravity, flow down the condensate pipe 24, past the check valve 25, and through the conduit 26 to the condensate tank 27 where it collects.

In accordance with the invention the check valve 25 is designed to prevent any evaporated condensate from passing back up through the conduit 24 to the condenser 16. The bleeder line 29 on the other hand is provided to equalize the pressure between the condensate tank 27 and retort 10 so that there will not be a pressure differential existing between these two chambers. If such a pressure differential did exist it would hold the check valve 25 closed and prevent liquid condensate from passing into the condensate tank 27. The bleeder line 29 is of sufficiently small inside diameter as to substantially prevent any flashing back of the condensate liquid through it, but is of sufliciently large diameter to insure equal pressures in the retort and condensate tanks.

Fig. 2 is an enlarged elevational view partly in section of the check valve 25 shown in Fig. 1.

As shown in Fig. 2 the valve 25 comprises a housing 30 secured at one end to pipe 24 and at its other lower end to pipe 26. Housing 30 defines interiorly an annular valve seat 31, the axis of this seat being coaxial with the pipes 24 and 26.

A valve closure member in the form of a flat plate 32 is pivotally suspended from the housing as at 33. At the known angle of inclination of the valve and connecting pipes with respect to the horizontal the closure member is designed to normally be gravity biased to just rest against the valve seat 31. The suspension of the closure member is thus critically adjusted so that only t the minutest of forces against the closure member will cause it to swing about its suspended pivot point to open the valve. After cessation of such force, the closure member 32 will assume its stable position (when its center of gravity is directly below the pivot point 33) wherein it just barely engages the valve seat 33.

In the operation of the condensate system, evaporated moisture from the perishables 11 is passed into the condenser chamber 16 with the aid of blower 13 and the action of the vacuum pump 19. This vapor upon contacting the refrigeration pipes 17 will condense and collect at the bottom of the chamber, passing down conduit 24, to the check valve 25. The weight of this condensate liquid is sufiicient to swing the closure member 32 away from the valve seat 31 permitting the liquid to continue down conduit 26 to the condensate tank 27.

Since the pressure in the condensate tank is substantially equal to the pressure in retort 10 and condenser 16 due to the various conduits interconnecting these chambers, the condensate liquid in tank 27 will have a tendency to flash or evaporate, especially since this tank is spaced from the colder refrigerated condenser tank.

Without check valve 25 then, this evaporated liquid would pass back up the conduit 24 to the condenser where it would again condense. Such action not only greatly increases the rate of frost built up on the pipes 17 but additionally tends to cause frost formation within the conduit 24 thereby restricting the free flow of condensate therethrough. The latter frost develops as a result of the re-evaporation of the liquid condensate.

The provision of the check valve prevents the flashing back of this re-evaporated moisture, but in order that the valve itself will not appreciably impede the flow of condensate to the tank 27 it is important that the pressure existing on each side of the closure member 32 be substantially equal.

The bleeder line 29, as described above, is provided for this purpose. It will permit the pressure in tank 27 to equalize to that in retort 10 which pressure is equal to the pressure in condenser 16 by virtue of the communication of these chambers by way of conduit 14, blower 13, and conduit 15.

It is seen accordingly that by incorporating the check valve and bleeder line in a novel combination with the principal elements of the precooling vacuum apparatus, there results greatly improved overall operating efficiency, and the detrimental effects of frost formation in the conduits of the condensate system is substantially eliminated.

I claim:

1. In a vacuum cooling system having vacuum chamber means for receiving products to be cooled and having condensing means for condensing water vapor evaporated from such products, a system for removing condensate from said chamber means comprising a pipe extending downwardly from a region of said chamber means in which such condensate collects, a check valve in said pipe normally biased to closed position, said check valve being operable to pass condensate by virtue of the weight thereof against the check valve, and a closed collector tank receiving condensate passed by said check valve, said check valve preventing water vapor resulting from flashing of the condensate within said tank from passing back into said chamber means.

2. The subject matter of claim 1, wherein said check valve comprises a valve seat and a downwardly opening closure member therefor lightly gravity biased to closed position, whereby small increments of condensate reaching said closure member are capable of opening the same against said light gravity bias.

3. In a vacuum cooling system having vacuum chamber means for receiving products to be cooled and having condensing means for condensing water vapor evaporated from such products, a system for removing condensate from said chamber means comprising a pipe extending downwardly from a region of said chamber means in which such condensate collects, a check valve in said pipe normally biased to closed position, said check valve being operable to pass condensate by virtue of the weight thereof against the check valve, and a pressure equalizing means between said tank and said chamber means to prevent said check valve from being held closed by reason of pressure diiferential between the interior of the chamber means and the interior of the tank.

4. The subject matter of claim 3, wherein said pressure equalizing means comprises a bleeder line.

References Cited in the file of this patent UNITED STATES PATENTS 2,344,151 Kasser Mar. 14, 1944 2,621,492 Beardsley Dec. 16, 1952 2,634,590 Beardsley Apr. 14, 1953 2,634,591 Beardsley Apr. 14, 1953 2,634,592 Beardsley Apr. 14, 1953 2,651,184 Kasser Sept. 8, 1953 

